The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Fractures in oilfield reservoirs typically have the highest flow capacity of any portion of the reservoir formation. In natural fractures, the high flow capacity results from the fracture being open and the closure stress being low. In artificially created fractures, the high flow capacity results from the fracture being propped with a permeable bed of material or etched along the fracture face with acid or other material that has dissolved part of the formation. Normally, such high flow capacity is desirable.
However, in the life of an oil well, there are various times in which it is desirable to reduce the flow capacity, by plugging or partially plugging the fracture. Typically, this is when the fracture is producing unwanted fluids such as water or gas, or there is a non-uniformity of injected fluid, or when expensive materials are being injected into non-producing areas of the formation. This is a particularly critical reason as at best the flow of expensive fluid into an already open fracture wastes the material, along with manpower, etc., to produce or increase a fracture where not needed, and in many cases, it results in the growth of a fracture into a region from which undesirable fluid, such as water, is produced. Compositions for plugging fractures to reduce flow of fluids and fluid loss have typically included clays or cement systems. The disadvantages of cements systems are the systems' inability to travel down the fracture without setting and bridging prematurely. The hydrating clays are complex to pump, and require expensive well work, they also must hydrate fully along the fracture and may also bridge prematurely.
Polymer systems have also been attempted for plugging fractures, but often fail due to lack of flow resistance. Further, use of such systems is expensive due to the requirements for large volumes of materials.
A need therefore remains for an inexpensive and reliable well plugging material and for methods of use during well treatments such as well completion, and stimulation, and also during fluids production.